Such a method and equipment to perform such a method are already known in the art, e.g. from the contribution to assist the Standards Committee T1-Telecommunications with reference T1E1.4/95-075. This contribution is entitled `How to use ADSL for more than 8 Mbps data?`, and is filed by Orckit Communications Ltd. Therein, a method for interleaving data frames, called interleave data frames, is proposed which enables ADSL (Asymmetric Digital Subscriber Line) transmission at bit rates higher than 8,16 Mbps. The proposed method is based on the insight that the specification in the draft American National Standard for Telecommunications on ADSL (Asymmetric Digital Subscriber Line) published by ANSI (American National Standards Institute) in April 1995, limiting the interleave frame size to the length of one codeword limits the transmission rate to a maximum of 8,16 Mbps. This transmission rate limitation is avoided by optionally including more than one codeword in one interleave data frame. In the known method, as described in the last paragraph on page 2 of the above mentioned contribution, an interleave data frame contains two words, and in a first step is split into these two words which may have different lengths. Each of the words in a further step is extended with an overhead extension, called FEC redundancy in the already cited contribution. The overhead extensions added to words with different lengths can also have different lengths. The so obtained codewords, called Reed-Solomon codewords in the above cited contribution, are then joined to constitute an extended interleave data frame which is written in an interleave buffer whose memory cells are fixed in a matrix-shaped structure in such a way that each extended interleave data frame occupies one column in the matrix-shaped structure. Since successive Reed-Solomon codewords in the known method can have different lengths, the required flexibility for the overhead adding means in a forward error correction device which is enabled to perform the known method, renders this overhead adding means more complex. Furthermore, in the known solution, the number of columns of the matrix-shaped structure in the interleave buffer remains unchanged when compared to interleaving techniques which are in accordance with the specifications in the above cited draft ADSL Standard and wherein each interleave data frame contains thus only one codeword. As a result, the interleave depth and correction capability for burst errors remains unaffected.